1. Field of the Invention
The present invention relates to an insulative material useful in microcircuitry applications, to a process of using the insulative material to prepare an integrated circuit, and to the integrated circuit obtainable thereby.
2. Description of Related Art
Low-k dielectric insulators are needed for, among other things, copper back-end-of-the-line (BEOL) on chip wiring in order to improve chip performance by minimizing crosstalk and capacitive coupling. The latter leads to substantial delays in signal propagation which becomes exacerbated as wiring dimensions decrease and densities increase. The difficulty of introducing any new material places a premium on dielectric extendibility, i.e., the use of materials with similar elemental compositions but with different dielectric constants for multiple device generations. The only true dielectric extendibility comes from the introduction of porosity. The introduction of porosity, while good for the reduction of dielectric constants, negatively impacts many other important material properties (electrical, thermal, mechanical).
Mechanical issues are particularly important for organosilicates, including chemical vapor deposition (CVD) and spin-on (SO) materials, which are intrinsically brittle materials and prone to cracking. Since organosilicates constitute, by far, the largest class of materials under consideration, mechanical issues move to the forefront because of concerns about reliability. The mechanical properties of these insulating materials are further compromised by the introduction of porosity to lower the dielectric constant. The mechanical properties of organosilicates have been addressed with limited success by variation in resin and/or porogen structures, control of porous morphologies and post porosity treatment using UV or e-beam exposure, usually at elevated temperatures. E-beam exposure has been shown to cause front end damage. For this reason, UV treatment of porogen/matrix nanohybrids or porous films generated by thermal calcination has become the method of choice for improving mechanical properties such as modulus and hardness.
Although improvements in modulii of 25–50% are sometimes achieved upon UV exposure, this requires a separate processing step and chemical changes are produced in the materials, which can degrade the electrical properties. Also, improved UV-efficiencies require specialized matrices and/or porogens for materials where the porosity is generated from sacrificial porogens. Although matrix structural modification can lead to improved modulii, this often occurs at the expense of dielectric constant, which, in turn, requires the addition of more porogen to achieve the dielectric target.
U.S. Pat. No. 5,895,263 describes a process for preparing an integrated circuit device comprising depositing a dielectric material comprising porous organic polysilica and a sacrificial porogen comprising a decomposable polymer onto a substrate. The entire contents of U.S. Pat. No. 5,895,263 are hereby incorporated by reference.
There still remains a need in the art to discover other materials that provide excellent dielectric properties without sacrificing mechanical properties.